Dimension-selective attention and second language acquisition

在全球化的世界中，越来越多的成年人移居到一个新的国家，并试图学习第二语言(L2)。不幸的是，许多二语学习者最终产生了严重的口音，难以理解。了解第二语言学习困难的根源可能会导致旨在提高学习困难学习者的第二语言技能的补救方法。语言结构是通过一组复杂的声音提示来传达的，包括持续时间、幅度和频率的变化。那些能够更好地识别这些声学线索的人可能能够更快地吸收一门新语言的结构。然而，由于不同语言在声音模式如何传达语言结构方面的差异，检测第二语言的声学提示可能会很困难。例如，在普通话等声调语言中，音高是词义的重要线索，但在英语等非声调语言中，它扮演着次要的角色。因此，音调对说普通话的人来说可能是一块“注意力磁铁”：当他们学习感知英语语音时，他们可能很难学会忽略音调，关注其他更相关的特征。那些能够更好地将注意力集中在单个声学维度上的人可能更能专注于在第二语言中提供最可靠信息的声学线索。我们建议检验一种假设，即与以英语为母语的人相比，说普通话的人很难将注意力从音高转移到其他声学维度上，从而在英语言语的感知和产生过程中过分重视音高。我们将使用EEG来检测当参与者被动地听复杂的音调流或被要求注意一个维度时，参与者的神经反应对音调与音色变化的编码程度。我们还将检查神经缠绕对音调轮廓和幅度包络的影响，同时受试者听自然主义的口头叙述。我们预测，与英语母语者相比，说普通话的人不仅在被动和自然的听力条件下，而且在被要求注意音色时，都会表现出更好的音调跟踪。此外，我们预测，那些能够更好地抵制音调并成功注意音色的普通话参与者也会表现出更多母语风格的英语语音输出。最后，我们将使用功能磁共振成像来研究语音感知过程中注意声学维度的神经网络；我们预测，在扫描仪中对语音进行分类的普通话说话者将在前额叶皮质和与音调感知相关的听觉皮质区域之间显示出更强的联系。我们进一步建议训练普通话说话者抵抗注意磁铁，将注意力引导到语音感知过程中其他有用的信息源。参与者将在几个月内完成九次培训，在培训中，他们将根据各种线索(除了音调)对言语特征(如重音或词义)进行分类。控制组将完成一系列词汇提升练习。我们预测，在接下来的几个月里，实验训练组将获得更接近母语的言语感知策略和更准确的发音。此外，我们预测，实验培训将提高参与者将注意力引导到语音中的声音维度的能力，这是使用脑电测量的。这个项目将使我们更好地理解为什么有些人比其他人更难学习第二语言。这可能会导致第二语言能力测试的发展，这种测试可以更准确地预测谁在成年后最容易掌握一门新语言。此外，该项目还可能导致制定干预措施，通过教学习者注意言语中最相关的方面来促进糟糕的第二语言学习。

In a globalized world, a growing number of adults are moving to a new country and attempting to learn a second language (L2). Unfortunately, many L2 learners end up producing heavily accented speech and struggling to comprehend speech. Understanding the sources of L2 learning difficulties could lead to remedial approaches designed to boost L2 skills in struggling learners. Language structure is conveyed by a complex set of acoustic cues, including changes in duration, amplitude, and frequency. Individuals who are better able to detect these acoustic cues may be able to more rapidly absorb the structure of a new language. However, detecting the acoustic cues of an L2 can be difficult, due to differences across languages in how sound patterns convey language structure. For example, in tone languages such as Mandarin, pitch is a vital cue to the meaning of words, but it plays a more secondary role in non-tonal languages such as English. As a result, pitch may be an "attentional magnet" for Mandarin speakers: they may have difficulty learning to ignore pitch and attend to other, more relevant features when learning to perceive English speech. Individuals who are better able to direct their attention to individual acoustic dimensions may be better able to focus on the acoustic cues which provide the most reliable information in an L2.We propose to test the hypothesis that Mandarin speakers, compared to native English speakers, have difficulty directing attention away from pitch and towards other acoustic dimensions, and thus place undue importance on pitch during English speech perception and production. We will use EEG to examine the extent to which participants' neural responses encode changes in pitch versus timbre when participants listen passively to complex tone streams or are asked to attend to one dimension. We will also examine neural entrainment to pitch contour versus amplitude envelope while participants listen to naturalistic spoken narratives. We predict that Mandarin speakers will show greater pitch tracking compared to native English speakers not only in the passive and naturalistic listening conditions, but also when asked to attend to timbre. Moreover, we predict that Mandarin participants who are better able to resist attending to pitch and successfully attend to timbre will also demonstrate more native-like English speech production. Finally, using fMRI, we will investigate the neural networks underlying attention to acoustic dimensions during speech perception; we predict that Mandarin speakers categorizing speech in the scanner will show stronger connections between pre-frontal cortex and regions in auditory cortex linked to pitch perception.We further propose to train Mandarin speakers to resist the attentional magnet, directing attention towards other useful sources of information during speech perception. Participants will complete nine sessions of training over several months in which they will categorize speech features (such as stress or word meaning) on the basis of various cues besides pitch. A control group will complete a series of vocabulary boosting exercises. We predict that over the course of the following months, the experimental training group will achieve more native-like speech perception strategies and more accurate pronunciation. Furthermore, we predict that the experimental training will improve participants' ability to direct attention to sound dimensions in speech, as measured using EEG.This project will lead to a better understanding of why some people struggle to learn a second language more than others. This could lead to the development of second language aptitude tests which more accurately predict who will most readily acquire a new language in adulthood. Moreover, this project could also lead to the development of interventions designed to boost poor second language learning by teaching learners to attend to the most relevant aspects of speech.